Graphene, a two-dimensional carbon atom sheet, has attracted tremendous attention and research interest because of its exceptional physical properties. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. The main focus so far has been on fundamental physics and electronic devices. However, because the linear dispersion of the Dirac electrons enables ultrawideband tunability, we believe its true potential lies in photonics and optoelectronics. In this review, we introduce recent advances in the nonlinear optical properties of graphene-based materials. The rise of graphene in nonlinear optics is shown by several recent results, ranging from saturable absorbers and the four-wave mixing effect to giant two-photon absorption, reverse saturable absorption and optical limiting. The relevant forms of the graphene-based materials include pure graphene, graphene oxide and graphene hybrids.